1. Technical Field
The present invention relates to a sheet-guiding unit separating system, a fixing device with the sheet-guiding unit separating system, and an image forming apparatus with the fixing device with the sheet-guiding unit separating system. In particular, the present invention relates to a sheet-guiding mechanism to guide a recording medium discharged from a fixing nip of a fixing device, a fixing device with the sheet-guiding mechanism, and an image forming apparatus with the fixing device with the sheet-guiding mechanism.
2. Related Art
In the past, various types of image forming apparatuses, such as copiers, facsimiles, printers, etc., using an electrographic system have been proposed and well known. In the image forming apparatus, the following steps generally establish an image forming process. An electrostatic latent image is initially formed on a surface of a photoconductive (PC) drum serving as an image bearer. The electrostatic latent image on the photoconductive drum is then developed and rendered visible by toner or the like acting as a developing agent. The developed image is then transferred onto a recording medium (hereinafter, also variously sometimes referred to as a sheet, a recording sheet, a recording member, a transferring member) by a transfer device and is borne thereon. The toner image on the recording medium is then fixed onto the recording medium by a fixing device under pressure and heat or the like.
In the fixing device, a fixing member and a pressing member are opposed to each other as rotating members (e.g., rollers, belts, or a combination of each of them) while forming a nip (i.e., a fixing nip) therebetween. For example, in a roller type fixing device with an internal heater such as a halogen heater, etc., which forms the fixing nip by pressing a fixing roller (typically heated) and a pressing roller against each other, a recording medium bearing an unfixed toner image is conveyed through the fixing nip between these two rotating members (i.e., the fixing roller and the pressing roller) rotating in pressure with heat. The toner image is consequently heated and the pressed between these rotating members, and accordingly, melts due to the heat and is fixed on the recording medium.
Because the toner is mostly made of resin, and accordingly tends to melt in the fixing nip and adhere to a fixing member (e.g., a fixing roller and a fixing belt), the toner generally needs to be prevented from sticking to the fixing roller and the fixing belt or the like. Thus, there have been various attempts to prevent such sticking, such as adding wax compound to the toner, coating surfaces of the fixing roller and the fixing belt with releasable material, applying lubricant such as silicone oil, etc., to the surfaces of the fixing roller and the fixing belt, etc.
Further, a sheet separator with a separating nail (hereafter, sometimes collectively referred to as a separator, simply) may be attached to either a fixing roller or a fixing belt downstream, i.e., a sheet discharge side, of a fixing nip at a position immediately downstream of the fixing nip. The separator forcibly removes the recording medium that tends to wind around either the fixing roller or the fixing belt due to melting of the toner.
In recent years, to replace the separating nail, a sheet separator with a separating plate is sometimes attached to the fixing roller or the fixing belt across a narrow gap (i.e., separated therefrom). That is, a thin plate-like member is opposed to the fixing belt or the fixing roller immediately downstream of the fixing nip via the narrow gap not to avoid abrading the fixing roller or the fixing belt to avoid a problem caused by the separating nail.
Even so, the sheet separator, whether a separating nail, a separating plate, etc., cannot completely prevent the recording medium from winding around the fixing roller or the fixing belt. That is, when the separating nail or the separating plate is disposed close to the fixing roller or the fixing belt, and a sheet gets jammed, the jammed sheet is difficult to remove because it is usually is difficult to remove, because it is usually torn and/or partially left in a fixing device.
As a countermeasure against this problem, a sheet guiding unit separating system has been proposed to separate the separating nail, the separating plate, and a sheet guiding unit such as a guiding plate, etc., having the separating nail or plate, which is disposed in the sheet conveyance path immediately downstream of the fixing nip of the fixing roller or the fixing belt.
For example, in a conventional fixing device, more than one separating nail enabled to freely pivot around its shaft, a bracket having an elastic member, and a sheet ejection guiding unit having a lever, a pressing member, and a stopper nail pivoted by the lever are provided as a pivoting unit enabled to freely pivot around a prescribed axis of a fixing device. Further, the bracket unit is enabled to freely pivot around a fulcrum established in the above-described sheet ejection-guiding unit. Thus, when a sheet jam occurs and is to be dealt by operating the lever and pivoting the stopper nail unit away from a holder that holds a body of the fixing device, the pressing member presses against the elastic member to pivot the bracket unit so that the above-described sheet ejection guiding unit separates and allow access to the fixing nip. At the same time, a tip of the separating nail unit is separated from a surface of one of the rotating members.